Ciudad Mier, Mexico — Shell casings carpet the road outside a bullet-riddled subdivision on the outskirts of this colonial town on the Rio Grande Valley, abandoned by most of the 6,000 inhabitants following a nine-month battle by warring drug cartels.Nobody lives in the 65 one-story white houses across the border from Roma, Texas, except the abandoned pets that roam the streets of the Casas Geo development. Like 90 percent of those who once lived in Mier, they have fled to a shelter in the nearby city of Miguel Aleman, Mexico's first such haven for people displaced by drug violence.While Mexicans increasingly have fled border towns up and down the Rio Grande Valley, Ciudad Mier is the most dramatic example so far of the increasing ferocity of war between rival drug cartels, and the government's failure to fight back.The state and federal governments say it's safe to go back and that people are returning. One official even invited tourists to return. The scenes witnessed by The Associated Press say something else.Even during daylight hours, a Mexican army squad patrols the town nervously. A bullet-riddled army pickup truck lies in the yard of the local military outpost, a metallic casualty of an ambush last weekend that locals say killed four soldiers. The Army does not officially recognize it even happened.A man named Rogelio, 72, a migrant who retired after years of lawn work in Milwaukee, Wisconsin, and Chicago, has a question for them:"Where were they nine months ago?" He asked not to give his last name for fear of reprisals. Almost everyone in town has had a relative kidnapped by the gangs, he said. "We have had nine months of gun fights, almost every night. Why did they leave us alone?"Only about 400 people remain in the town. Most went to Texas or other Mexican cities. Some 300 others are staying in a Lion's Club-turned-shelter in nearby Ciudad Miguel Aleman with no intention of returning, even though the clean auditorium with tiled floors covered in foam mattresses doesn't feel much safer: A shootout a block away from the shelter sent them diving for cover last week.Terrified refugees lower their voices so as not to be heard by the cartel lookouts. A heavily tattooed young man with a flashy, embroidered baseball cap and gold chains lounges on the sidewalk outside and interrogates a reporter: What are you doing here? Who have you interviewed inside?Gabi, 18, a high school student at the shelter, nearly whispers that cartel gunmen left a man hanging by his neck from a palm tree in the Ciudad Mier town square in June."His face was taped over, and they had cut off his hands and legs," she said.About half the houses in Ciudad Mier have bullet holes. The Casas Geo subdivision seems frozen in time; most residents left in the summer, and it was empty by early November. The houses show how people lived when the battle reached its height: armoires and wooden wardrobes pushed up against the windows, in a vain bid to stop the bullets.Gaping holes in walls, windows and doors where high-powered ammunition made impact. On the entrance to the subdivision, someone daubed in paint "CDG" and a heart, a reference to the Gulf Cartel.Outside the entrance, abandoned cattle wait next to the roadside for a rancher. Dozens of ranchers have been kidnapped and killed by the cartels since the war broke out between the Zetas and the Gulf Cartel on Feb. 23. That is when the Gulf Cartel roared back into town to retake it from the Zetas; both see it as a lucrative trafficking route in a rural border area.Two lucky horses are quickly carted off; their owners are too nervous to talk, and speed away with the trailer bearing the animals. The only people returning to Ciudad Mier are stopping only briefly, to spirit off whatever possessions they can still rescue. One couple loads up everything they can rescue from their house — even the hot water heater — into their pickup before taking off. "It will be a year or two before I even think of returning," said the husband.In fact, it may be longer. The Zetas, sensing weakness, launched a new offensive after the Nov. 5 slaying of top Gulf cartel leader Ezequiel "Tony Tormenta" Cardenas Guillen. Most believe the Zetas are still lurking on the cattle ranches and in the brush and low woods around Ciudad Mier and farther up the Rio Grande valley, just waiting to return.Some hold out hope that kidnapped loved ones are still being held at the cartel hideouts."My father said, 'I'm going over to the ranch to cut some wood and pick up a few (fence) rails.' He never came back," said one middle-aged woman at the Lion's Club shelter.Maria Isabelle, 42, disappeared from the shelter and hasn't been heard from."A truck came by and someone said, 'Pick up that woman,'" said her mother, shelter resident Maria de la Luz, 59.In Casas Geo, another resident on a quick run to his former home shows a reporter a flame-scarred house across the street. "This is where they fired a rocket into the house," he said. He was picking up furniture from a house where the subdivision's last remaining holdout, Gaspar Rodolfo, was kidnapped earlier this month.Across the road, a feed-store owner tosses the twisted metal casing of a rocket-propelled grenade onto his counter. In the back room, he has a five-gallon bucket full of shell casings he collected in his parking lot.Farther down the road, a restaurant owner pours his own collection on the counter: casings from an M-40 grenade launcher, and .50-caliber bullets.But that probably isn't what scares the army, which has M-40 launchers and .50-calibers of its own. It's what lies in the municipal impound lot that is truly frightening. The burned-out remains of five crudely armored pickup trucks and SUVs, with half-inch steel plate welded over most of the windows, leaving only a narrow slit for the drug gunmen's visibility and firing. It all looks like something out of a "Mad Max" movie.Farther outside of town lies a homemade tank that locals refer to in hushed tones as "The Monster.""The Monster" was a 10-wheel gravel truck with a 5-yard (meter) freight box, entirely covered in 1 1/4-inch steel plate welded into the box to cover firing positions for about 10 gunmen. In the cab, the thick steel plate covered the engine, the windshield and the doors, punctuated by hinged covers for gun ports, and massive steel rams welded onto the prow of the craft.What is terrifying about "The Monster" was not that the Zetas drug gang built it and used it in the almost medieval war for Ciudad Mier, but that the Cartel del Golfo — which roared back into Mier with a vengeance on Feb. 23, 2010, to retake the turf — brought it down.Perhaps most frightening of all is what is happening farther up the road from the subdivision, where the highway leads toward the town of Nueva Ciudad Guerrero. Even those brave enough to sneak back into Ciudad Mier won't take the road to Guerrero, where 11 Zeta gunmen were killed in a clash with soldiers days before. In more than an hour's time, not a single vehicle passes in that direction.